1. Field of the Invention
The present invention relates to a current pinching type semiconductor light-emitting element suitably used in, e.g., an auto-focus light source for a camera, and a method of manufacturing the same.
2. Description of the Related Art
Recently, cameras tend to have auto-focus functions. In a ranging (distance measurement) operation to an object, for example, the principle of triangulation using light is employed. As a light source for the ranging operation, an LED as a semiconductor light-emitting element is used. One of characteristics and a current pinching type LED chip, and an enclosure difficult for a normal LED to meet this requirement, and a current pinching type LED chip, and an enclosure having satisfactorily optically designed lenses must be combined.
FIG. 1 shows a typical example of the current pinching type LED chip. An n-type GaAs current blocking layer 22, a p-type GaAl.sub.0.25 As.sub.0.75 cladding layer 23, a p-type GaAs active layer 24, an n-type GaAl.sub.0.25 As.sub.0.75 cladding layer 25, and an n-type ohmic electrode 26 are sequentially formed on the upper surface of a p-type GaAs substrate 21. Furthermore, a p-type ohmic electrode 27 is formed on the lower surface of the p-type GaAs substrate 21.
In an operation mode, a current is pinched by the current blocking layer 22, and is concentrated at the central portion of the active layer 24. Light emitted upon recombination in the active layer 24 is transmitted through the cladding layer 25, and is radiated outside the chip from an opening portion of the ohmic electrode 26. FIG. 2 is a plan view of this chip.
Normally, a portion, at the side of the substrate 21, of this chip is fixed to a frame or a stem using a conductive resin, and the ohmic electrode 26 on the cladding layer 25 is connected by bonding to the lead post of the frame or stem through a thin Au line. Therefore, a bonding region 28 surrounded by a dotted circle in FIG. 2 requires at least an area according to the bonding technique.
Since a so-called III-V Group compound semiconductor used in a GaAlAs-based infrared LED is a very expensive material as compared to Si, the chip area is decreased as much as possible to attain a low-cost structure.
However, since this LED chip has a more complicated structure than that of a normal chip, and is expensive, further miniaturization of the chip must be realized. A light-extraction opening portion 29 must have a predetermined area for satisfying required electrical and optical characteristics. In addition, as described above, the minimum bonding region 28 is required. Therefore, the remaining portion, i.e., a portion 30 surrounded by an alternate long and short dashed line in FIG. 2, may be omitted.
As shown in FIG. 1, however, some light components 31 of light emitted from a portion (current concentrated portion) of the active layer 24 propagate in the lateral direction, and leak from the side surface of the chip. This phenomenon is called "light leakage", and becomes a cause for impairing characteristics when the chip is used in an auto-focus light source for a camera. As the cladding layer 25 becomes thicker, current concentration is reduced, and light is also emitted from a portion near the chip edge of the active layer 24, thus increasing a light leakage portion. In order to avoid this, the light-emitting portion is separated from the chip edge by a certain distance. According to the experiments of the present inventors, the distance must be at least 130 .mu.m.
Therefore, in addition to the light-extraction opening portion 29 (light-emitting portion), and the bonding region 28, an area for preventing light leakage is also required. The portion 30 surrounded by the alternate long and short dashed line serves as light leakage prevention region. As a result, many restrictions are imposed on reduction or miniaturization of the chip.